Summary: Erythroid diseases associated with pathological growth include anemias, polycythemia, and erythroleukemia. In addition, there is evidence that several other disease entities that share a common feature of ineffective erythropoiesis are manifested by dysregulated erythroblast growth and apoptosis. The project includes the identification and characterization of growth-regulating genes and proteins that are expressed during erythropoiesis. In addition, small molecule screens are being preformed to identify candidate molecules that modulate the effects of erythropoietin upon erythroblast growth and differentiation.